WSO October 2023 – Issue 1 - 949

Yang et al.
949
Introduction
Statins have been widely reported to be effective cholesterol-lowering
drugs, reducing mortality and the risk of cardiovascular
events.1,2
Although
many
cardiovascular
benefits
of statins have been recognized, concerns have
been raised that statin therapy might be associated with an
increased risk of intracerebral hemorrhage (ICH), particularly
for those with cerebrovascular events.3-5
Evidence from existing studies is inconsistent, with statin
use in patients with ischemic stroke (IS) reported to be
unrelated to6,7 or protective against ICH.8 However, the
potential risk of ICH with high-intensity statin therapy was
documented.5,9 Until now, high-intensity statin therapy has
been advocated for post-stroke treatment, but the effect of
statin intensity on ICH after IS remains controversial.
Several studies suggest that the higher risk of ICH with
high-dose statin therapy should be noted, especially in
patients with IS after thrombolytic therapy,3,9 while others
do not yet support such a dose-response association.6 In
addition, different statins differ in terms of clinical efficacy
and side effects.5,10 Rosuvastatin has been reported to be
superior to atorvastatin in the prevention of cardiovascular
events, suggesting that rosuvastatin may be superior to
atorvastatin in patients at high cardiovascular risk.11-13
However, to date, evidence to support tailoring the type or
dose of statins for safety concerns of ICH is limited, especially
in the treatment of patients with IS.14
Globally, East Asia had the highest incidence rate of IS
and the most pronounced increase, especially in China,15
resulting in a huge population of disability and a serious
economic burden.16 However, evidence from large-scale
population studies on the association of post-IS statin therapy
with ICH is lacking. Therefore, this study aims to
assess the relationship between the use, intensity, and type
of statins and ICH readmission in patients with newly diagnosed
IS in Beijing, a megacity in China, from 2010 to
2017.
Methods
Data source
Details of the Beijing Medical Claim Data for Employees
(BMCDE) database have been previously described elsewhere.17,18
Briefly, anonymous medical claim data, such as
demographic characteristics, clinical diagnosis, medication
and reimbursement information, of all active or retired
employees enrolled in basic medical insurance in Beijing
(nearly 90% of Beijing's permanent population) were registered
into the database. Because the data we used were
retrospective information encrypted for administrative purposes,
our research was exempt from ethics committee
review.
Study population
We included patients ⩾18 years of age with newly diagnosed
IS and documented hospitalization who were enrolled
in Medicare between 2010 and 2017. Clinical diagnostic
information was presented in the International Classification
of Disease edition 10 (ICD-10) code, as well as descriptive
texts. IS was identified by ICD-10 coding (I63) or text
diagnosis. " Newly diagnosed " was defined by applying a
fixed 24-month look-back period in which the patient had
continuous data coverage but did not have any records of
IS. The earliest registry hospitalization of IS was used as
the index hospitalization for patients with multiple registry
hospitalizations. To explore the effect of post-stroke statin
therapy, eligible patients had no records of statins or other
cholesterol-lowering drugs (fenofibrate, niacin, probucol,
etc.) in the 12 months prior to the first diagnosis of IS.
Subjects were excluded if they (1) had a previous history of
primary diagnosis of hepatic failure (ICD-10: K70-K72 or
text diagnosis, N = 20) or severe kidney disease (ICD-10:
I12; I13; N00-N05; N07; N11; N14; N17-N19; Q61 and
text diagnosis, N = 804) and (2) died within a month
(N = 1491).
Statin exposure
Drug information includes brand and generic drug names,
formulations, costs, and dispensing dates. The primary
exposure variable was any statin prescription within
1 month of the first documented stroke diagnosis. Among
patients who received any statin therapy, secondary exposure
variables were high versus low/moderate intensity of
statin use and types of statin adherence. High-intensity statin
therapy was defined as atorvastatin ⩾ 80 mg, simvastatin
⩾ 80 mg, pravastatin ⩾ 40 mg, and rosuvastatin ⩾ 20 mg
per day or equivalent combination.3,19 Low/moderateintensity
statin therapy was defined as all other statin
agents. Types of statin adherence were indicated by the proportion
of days covered (PDC) ⩾ 80% for each type of statin
during follow-up20,21 (PDC = days covered by the
prescription/days between the first prescription fill date and
the end date).22 Patients who adhered to two or more types
of statins were not considered in the analysis of the effects
of different types of statins.
Ascertainment of outcome
ICH readmission was defined as receiving any records of
ICD-10 code diagnosis (I60-I62) or text diagnosis after IS.
Information on deaths was obtained from the Medicare
Death Registry. Patients were followed from the date of IS
diagnosis (baseline) until the earliest ICH event occurred,
death, withdrawal from the database, or termination on 31
December 2017, whichever occurred first.
International Journal of Stroke, 18(8)
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